COMPLEX OXIDE, METHOD FOR PRODUCING SAME AND EXHAUST GAS PURIFYING CATALYST

Disclosed are a silicon-containing cerium composite oxide which is capable of maintaining a large specific surface area even used in a high temperatures environment, and which has excellent heat resistance and reducibility, as well as a method for producing the composite oxide and a catalyst for exhaust gas purification employing the composite oxide . The composite oxide contains 2 to 20 mass% silicon in terms of SiO, has properties of exhibiting a specific surface area of not less than 40 m/g as measured by the BET method after calcination at 1000 °C for 5 hours, and a reducibility of not lower than 30 % as calculated from measurement of temperature-programmed reduction from 50 °C to 900 °C after calcination at 1000 °C for 5 hours, and is suitable for a co-catalyst for a catalyst for exhaust gas purification.